Field of the Invention
Embodiments of the present invention relate generally to a blanking aperture array device for multi-beams, and to a method for fabricating a blanking aperture array device for multi-beams.
Description of Related Art
In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits progressively narrows year by year. In fabricating a mask used in a lithography technique which forms such a circuit, an electron beam writing technique having high resolution is employed.
As a writing apparatus that performs electron beam writing, a writing apparatus using multi-beams can be cited. Compared with the case of writing a pattern with a single electron beam, since in multi-beam writing it is possible to irradiate multiple beams at a time, the throughput can be greatly increased. For example, in a writing apparatus employing a multi-beam system, multi-beams are formed by letting portions of an electron beam emitted from an electron gun pass through a corresponding hole of a plurality of holes formed in the mask, and the multi-beams are made to pass through respective blanking aperture devices to be individually blanking-controlled. In that case, each deflected beam is blocked (blanking) by a blocking member, and each undeflected beam irradiates a target object or “sample”. At this time, blanking control is performed for each beam by a deflection means other than the blanking aperture array device so as to irradiate a desired position on the target object.
In the blanking aperture array device for performing blanking control of multi-beams, there are formed a plurality of passage holes for multi-beams, wherein a pair of electrodes for deflecting a beam is formed at the circumference of each of the passage holes. For the blanking aperture array device, a manufacturing method of forming each passage hole, each electrode pair, etc. in/on a silicon (Si) substrate by using a semiconductor manufacturing technique is employed.
If a protection insulating film is exposed on the surface of a fabricated blanking aperture array device, the exposed insulator on the surface is charged (electrified) due to irradiation of beams emitted by the writing apparatus incorporating the blanking aperture array device. Therefore, there is a problem that beam distortion or blur occurs because of the electrostatic charge. Thus, antistatic measures need to be taken for the blanking aperture array device. For example, electrodes of the pair are formed to be at opposite sides of the passage hole formed in the Si substrate in a manner such that the side wall of the passage hole is incorporated in the electrode pair, and a metal wiring from each electrode is formed on the substrate. Regarding the metal wiring, there is disclosed a structure in which a metal film is applied, through an insulating film, on the metal wiring so that electric potential of the wiring may not affect the beam deflection (e.g., refer to Japanese Patent Application Laid-open (JP-A) No. 2005-136114). Besides, there is disclosed a structure of a blanking aperture array device in which an insulating film is exposed over the electrode region of the substrate body, and an electrode having been fabricated as another substrate is bonded to the substrate body where the surface of the insulating film is covered with a metal film (e.g., refer to Japanese Patent Application Laid-open (JP-A) No. 2010-267962). However, in whichever of the above structures, since there remains an insulator on the upper surface of the blanking aperture array device, it is impossible to perfectly inhibit electrostatic charge of the insulator at the time of beam irradiation. Moreover, it is difficult to sufficiently achieve the charge inhibiting effect in the structure where an Si (semiconductor) substrate is exposed intact in the region other than the electrodes, wiring points, etc. Further, in the case of forming an electrode on the side wall of the passage hole, or bonding an electrode fabricated as another substrate, it makes the fabrication of the blanking aperture array device complicated.